Experimental Investigation and Numerical Characterization of Heating Cable Situated in Conduit

Heating cables inserted in metal conduit that is embedded in concrete are used in frost heave prevention of liquefied natural gas storage tanks (LNG tanks). The subfreezing temperature of the tank can cause the soil below and around it to freeze. This phenomenon causes heaving of the soil and damage to the foundation of the tank. This study investigates both the worst heat transfer scenario, where the heating cable is positioned in the center of and not in direct contact with the conduit, and the best heat transfer scenario, where cable is positioned on the bottom of and in direct contact with the conduit, for the purpose of preventing frost heave of the tank. Experiments are carried out to evaluate the cable power output and sheath temperature under a variety of conduit temperatures and applied voltages. A coupled thermal-electric-fluids numerical model is developed as well in Ansys-CFX to predict the cable power output and its temperature distribution. The numerical model is calibrated and the predicted cable power output and cable sheath temperature are compared with the experimental data. The numerical predictions demonstrated good agreement with experimental data. The heat transfer mechanism between cable and conduit involves thermal conduction, convection and radiation.